sql server如何利用开窗函数over()进行分组统计

declare @t table(
ProductID int,
ProductName varchar(20),
ProductType varchar(20),
Price int)

insert @t
select 1,'name1','P1',3 union all
select 2,'name2','P1',5 union all
select 3,'name3','P2',4 union all
select 4,'name4','P2',4

select t1.*
 from @t t1
 join (select ProductType,
 max(Price) Price
 from @t
 group by ProductType) t2 on t1.ProductType = t2.ProductType
 where t1.Price = t2.Price
 order by ProductType

;with cte as(
 select *, max(Price) over(partition by (ProductType)) MaxPrice
 from @t)
select ProductID,ProductName,ProductType,Price from cte where Price = MaxPrice
 order by ProductType

WITH OrderInfo AS

(

 SELECT ROW_NUMBER() OVER(PARTITION BY EmployeeID ORDER BY OrderDate) AS Number,

 OrderID,CustomerID, EmployeeID,OrderDate FROM Orders (NOLOCK)

)


SELECT Number,OrderID,CustomerID, EmployeeID ,OrderDate

From OrderInfo WHERE Number BETWEEN 0 AND 10

WITH OrderInfo AS

(

SELECT COUNT(OrderID) OVER(PARTITION BY EmployeeID) AS TotalCount,OrderID,CustomerID, EmployeeID,OrderDate FROM Orders (NOLOCK)

)

SELECT OrderID,CustomerID, EmployeeID ,OrderDate,TotalCount

From OrderInfo ORDER BY EmployeeID 

WITH OrderInfo AS

(

 SELECT COUNT(OrderID) OVER() AS Count,OrderID,CustomerID, EmployeeID,OrderDate FROM Orders (NOLOCK)

)